Selective system



Dec. 29, 1942. w. H. T. HOLDEN 2,306,382

SELECTIVE SYSTEM Filed March 11, 1941 3 Sheets-Sheet l INVENTOR y W H.7THOL DEN A TTORNEV Dec. 29 1942. w. H. T. HOLDEN SELECTIVE SYSTEM FiledMarch 11, 1941 3 Sheets-Sheet 2 A TTORNEV FIG. 3.

Filed March 11, 1941 3 Sheets-Sheet 3 a. I *1 I Q 55, WM/H INVENTORWHTHOLDEN I A rom/5 Patented Dec. 29, 1942 SELECTIVE SYSTEM William H.T. Holden, Woodside, N. Y., assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York ApplicationMarch 11, 1941, Serial No.. 382,731.

5 Claims.

This invention relates to the selection and identification of lines,trunks, circuits or other electrical devices.

An object of the invention is to enable the selection and identificationof lines or other circuits from a group with a minimum of interferenceand error.

Another object is to accomplish this purpose at increased speeds andwith a minimum amount of connecting and controlling equipment.

It is often necessary in switching systems, particularly in telephonesystems, to identify desired lines or other circuits in a group and toset up registrations or indications in accordance with the digitalcharacters of their designations. If two or more lines require selectionand identification at the same time, diificulty is likely to arise wherethe lines are arranged in coordinate groups and coacting mechanisms areused for selecting the lines. For instance, a group of one hundred linesmay be divided into ten groups of ten each, appearing in coordinate rowsin a switching mechanism for selection and identification by their tensand units digits. A single line is readily selectable by determining itstens and units rows. However, if attempt is made to select two linessimultaneously, double connections are likely to occur since all tensrows are in coordinate relation with all units rows. To

obviate these false operations complicated and expensive mechanisms havebeen required in the past.

According to the present invention the foregoing objects are realizedand advantages are obtained over selecting systems used in the past bymeans of a selecting and identifying system in which two groups ofdischarge devices or tubes serve to select and to identify accuratelyany line in a plurality of groups which may contain a pluralit of linescalling simultaneously for attention. More specifically, the successivedischarge tubes of the first group correspond to the tens digitaldesignations of successive groups of lines; and the tubes of the secondgroup correspond to the successive units designations of the lines ineach one of the tens groups. The lines of each group appear in theelectrodes of the corresponding tens tube and in the electrodes of theten corresponding units tubes, and no connecting medium is required forassociating the lines of one group with the tubes to the exclusion ofother groups. Both the tens and units tubes are rendered operative bythe calling condition on the lines and by the application during theexistence of this condition of phase impulses, the

impulses of the successive phases being applied respectively to thesuccessive tens and units tubes in the groups. When, therefore, acalling condition occurs on one or more lines. in one or more groups, atens tube corresponding to one of the calling groups discharges inresponse to the application of the phase impulse and instantly disablesthe remaining tenstubes to:- prevent av second one from discharging. Thedischarge of the operated tens tube conditions. for operation all units.tubes corresponding to calling lines in the. chosen tens group. As soonthereafter as a phase impulse is applied to a units tube in which acalling. line appears, the tube discharges and in.- stantly: disablesthe. remaining units tube. Thus only one tens tube and only one unitstube rep-- resenting the digital. characters of one calling line may bedischarged, although other lines are calling simultaneously. Thedischarged tubes cause the. operation of associated relays to reg;-ister the designation or otherwise to indicate the identiy of thecalling line.

A. feature of the invention is a tube control system in which theoperating potentials applied to the. electrodes of the units tubes arethe result of potentials produced by a discharged tens tube and thepotentials appearing on calling lines. With this arrangement it isimpossible for any one of the units tubes to discharge until a tens tuberepresenting one or more calling lines has operated and renderedineffective the remaining tens tubes. Thus the identification ultimatelyobtained will always be the true designation of some particular callingline and will not include one digit of one line and another digit ofanother line.

These and other features of the invention will be discussed more fullyin the following detailed specification.

In the drawings accompanying the specification:

Fig. 1 illustrates a plurality of subgroups of lines from whichselection is made;

Fig. 2- (-placedbelow Fig. 1) shows two series of selecting tubes, oneseries pertaining to the line groups and theother series pertaining; tothe lines of each group. This figure also illustrates an impulseproducing mechanism: for: operating" the tubes and anindicating orregistering mechanism for receiving the registration of the. selectedlines; and

Fig. 3 shows an alternative form of the circuits for operating theselecting tubes.

The selecting system disclosed herein, which e comprises series of spacedischarge tubes correspending to the designation characters of lines,links, trunks, or other circuits, may be used for a wide variety ofpurposes. For example, it may serve to select calling lines or trunksand to extend these lines or trunks to available outgoing circuits; itmay serve to select idle lines from a group of equivalent lines forserving incoming calls; and it may serve to establish an indication ofthe designation of lines, trunks, or other circuits for messageregistration purposes or for the information of operators.

Although the invention is not necessarily limited to selection fromgroups of any particular size, it is illustrated herein as applied to asystem for making selections from a group of one hundred lines. Theselines are divided into ten digital groups I00, IOI, I09. Group I is theNo. 0 tens group, that is, the group in which the tens digit of all tenlines is 0. Group IOI is the No. 1 tens group, and group I09 is the No.9 tens group, the intervening seven groups having been omitted to avoidunnecessary repetition. The ten lines of each of these groups have theten successive units digits 0 to 9.

The lines of all ten groups appear in the electrodes of the two seriesof selecting tubes 260 and 210. There are ten tubes in the tens series260, these tubes corresponding respectively to the ten tens groups oflines. For example, tubes 200, I, 209 correspond respectively to thegroups I00, IOI, I 09. Each tube has a main anode, a cathode and tenstarting electrodes. The ten starting electrodes are connectedrespectively to the test conductors of the lines of the associatedgroup. Likewise each of the ten units tubes is equipped with a mainanode, a cathode and ten starting electrodes. The ten startingelectrodes of each units tube are connected respectively to the testconductors of the ten lines having the same units designation. Forexample, the ten electrodes of the No. 0 units tube 2 I 0 are connectedto the lines, one in each group, having the units digit 0. In the samemanner the No. 1 units tube 2| I has its starting electrodes connectedto the lines having the units digit 1; and the No. 9 units tube 2I9 hasits starting electrodes connected to the lines having the units digit 9.

The cathodes 202, 203, 204 of the ten tens tubes 260 are connected toindividual relays 205, 206, 201 and. thence through the common inductor208 to ground. Similarly, the cathodes 2I2, 2I3, 2I4 of the ten unitstubes 210 are connected through individual relays 2 I 5, 2 I 6, 2 I Iand thence through the common inductor 2 I 8 to ground. The anodes ofall tubes in the tens and units groups are connected over a commonconductor 220 through the contacts of control relay 22I to the positivepole of battery 222.

The voltage for ionizing the tubes is obtained by the simultaneousapplication of potentials to the control electrodes and the maincathodes. Whenever it is desired to select one of the lines, a positivepotential is applied to the test conductor thereof and over thisconductor to the corresponding start electrodes of the correspondingtens and units tubes. This potential, however, is insufficient tooperate either tube. The full ionizing voltage for the tens tubes isobtained by applying momentary impulses of negative potential to thecathodes during the time the starting electrodes are at positivepotential. These impulses are produced by an impulse generator 250 whichis energized by a source of alternating current 25I of any suitablefrequency. The generator 250 produces ten negative impulses, oftendifferent phases, per cycle of the source 25I and applies these impulsesover ten impulse conductors 252 to the cathodes of the respective tenstubes 260. Since these negative potential impulses are impressedconsecutively upon the cathodes of the tens tubes 260, only one tube ata time will have full operating voltage applied to its starting gap.This insures that only one tube will operate, in the event a pluralityof lines in difierent groups are in a calling condition at the sametime. As soon as any one of the tens tubes discharges, current flowingin the common inductor 208 produces a voltage drop which lowers thepotential applied to the cathodes of all tubes and prevents theionization of another one thereof.

The impulse generator 250 may be of any suitable type, such as thegenerators disclosed in the application of W. H. T. Holden, Serial No.361,536, filed October 17, 1940, and the patents to Holden, 2,285,815 ofJune 9, 1942, and 2,252,766 of Aug. 19, 1941.

The units tubes 210 are operated by voltages resulting from potentialsimpressed upon the starting electrodes by the calling lines and by thestarting electrodes corresponding to calling lines in the operated tenstube and potential impulses impressed upon the cathodes of the unitstubes by the impulse generator 250. The voltage resulting from thepositive potential applied by a calling line to the starting electrodeof a units tube and the negative potential impulse appliedsimultaneously to the cathode by the generator 250 is not suificient tooperate a units tube, as it was in the case of a tens tube. However,since some one of the tens tubes has already operated, the dischargecurrent flowing in the anode-cathode circuit raises the potential of allstarting electrodes, connected to lines having the calling potentialsthereon, to a positive value somewhat higher than that of the callingpotential source. Since these electrodes of the operated tens tube areconnected to corresponding starting electrodes in the units tubes, theseunits tubes have their starting electrodes raised to a positivepotential which is sufficient to ionize the tube as soon as the negativepotential impulse is applied to the cathode. Therefore, as soonfollowing the ionization of the tens tube as the negative phase impulseis applied to a units tube which has been conditioned for operation bythe operated tens tube, said units tube ionizes, and current flows inthe main anode-cathode circuit. The flow of current in this circuit andthrough the inductor 2I8 produces a voltage drop which is immediatelyapplied to the cathodes of the remaining units tubes to prevent theionization of a second one thereof.

Thus it is possible to operate only one of the tens tubes and only oneof the units tubes in response to a selectable condition on any one oron any plurality of lines. The operated tens tube results in theoperation of the corresponding relay in the cathode circuit, and theoperation of a units tube results in the operation of its individualrelay. These relays serve to operate registers or other devicesassociated with the mech-,

anism 253 for the purpose of causing the automatic selection of thechosen line or for preparing information for message registration or fordisplaying the identity of the line at operators positions. For example,the register mech-' anism 253 may serve to control the operation of;automatic switches I03, I 04, I05, to eigtend the selected line tooutgoing circuits.

The detailed operation of the selecting system will now be described.Assume for this purpose that calling or selectable conditions are placedsimultaneously on lines IE and till in the tens group it?!) and on lineI68. of the tens group IllI. These conditions may be applied by theoperation of the individual relays Iii), Ill and H2. When relays H8 andHI operate, circuits are closed from the positive pole of battery i !5,through the contacts of these relays and resistors H3 and [Hi to ground.A positive potential is thus applied through resistor H'I to thestarting electrode 223 representing the line H36 in the tube 200. Alsopositive potential is applied over resistor lit to the startingelectrode 22d representing line in! in the tube. 290. Likewise theoperation of relay H2 closes a circuit from positive pole of battery I59through resistor lit to ground, and positive potential is applied overthe resistor I2Il to the start electrode 225 representing the line H18in the tens tube 2E6. Thus positive potential is applied at about thesame time to three starting electrodes. two of which are in the No. 0tens tube 238 and the other of which is in the No. l tens tube 29L If atthis time the impulse generator 25.53 has already delivered a phaseimpulse over circuits 25 i and 255 to the tubes 2.00 and 20!,respectively, and is in the process of delivering impulses to thesucceeding tubes in the group 256, neither of the tubes 2&6 and 2d! canoperate until the source 25i enters its next cycle to repeat the phaseimpulses. When, however,- the next cycle commences, a potential impulseis applied through condenser 25% and resistance 257 and conductor 2% tothe cathode 202 of the tube 26.53. This momentary impulse applied to thecathode 2% is of negative potential, and the voltage produced across thegap formed by the cathode 222 and the start electrodes 223 and 224causes the tube to ionize. Immediately that the tube ionizes currentflows in a circuit from the positive pole of battery 222, contacts ofrelay 222i, conductor 225), anode 22%, cathode E02, winding of relay205, inductor 298 to ground. The flow of current in the inductor 2%produces a voltage drop which results in the immediate application of apositive potential to the cathodes 293, 204 of the remaining tubes inthe group. Therefore, when the next phase impulse is applied overcircuit 255 to the cathode 283 a moment later, the positive potential onthe cathode 233 prevents discharge from transferring to the main anode233 even if the starting gap ionizes momentarily. Similarly, succeedingtubes in the group are prevented from operating in response to thenegative impulses in case their starting electrodes have been madepositive by a calling condition on the corresponding lines. As soon asthe discharge current flowing in the main discharge circuit of the tube2&0 reaches a steady state, the inductive drop across the inductor. 28Bdisappears, but the resistance of this common element produces a voltagedrop which maintains positive potential on the cathodes of the tenstubes to prevent a second. one from operating.

At the time relays I I0 and I I I operate the positive potential ofbattery H6 is applied to the starting electrodes 221 and 22B of theunits tubes 2H! and 2 I I. Also the operation of relay I I2 appliespositive potential from battery H9 to the starting electrode 229 of thetube 2| I. It will be noted that the impulse conductors 252 are alsoconnected to the cathodes of the ten units tubes 210. Therefore, theapplication of a phase impulse over con u torl'iil to .thecathode 2I2 oftube 2III produces a voltage across the starting gap between the cathode2I2 and electrode 221 which is equal to the sum of the negative impulsepotential applied to cathode 2I2 and the positive potential applied tothe electrode 221 and the same is true when an impulse of the next phaseis applied over conductor 259 to the cathode 2I3 of the tube 2H. But thestartinggaps of the units tubes require a higher voltage to produceionization than the corresponding gaps of the tens tubes. Hence theunits tubes do not ionize until some one of the tens tubes has operated.

When the tens tube 2% does operate, as above described, the startingelectrodes act as collectors in response to the flow of current withinthe tube and the potential of each starting electrode which represents aline having a calling condition thereon is raised to a valueconsiderably higher t a the potential applied as a result of the callingcondition. For instance, the positive potential of the electrodes 223and 225 is higher after current begins to flow within the tube than hepotential applied to these electrodes from the battery M5. Thus thepositive potential on the electrode 22? of the units tube 2th and thepositive potential of the electrode 228 of the units tube lIi are raisedto a value sufficient to cause ionization as Soon as a negative impulseis applied to the cathode of either one of these tubes. The positivepotential of the electrode 229 of the tube iii remains at the valuedetermined by the source I 99. After an interval following theconditioning of the units tubes Eid and 2H a negative impulse is appliedfrom the generator 3253 to the cathode of one of these tubes. As-

suming that the next impulse is applied to the cathode 252 of the tube2th, this tube ionizes its control gap, and immediately the dischargetransfers to the main anode of the tube. Current now flows in a circuitfrom the positive pole of battery 222, contacts of relay 22L anode 230,cathode 2512, relay 2%, common inductor 2H3 to ground. The inductivedrop produced by the element 2E8 alters the potential of the cathodes2I3, 2M of the remaining tubes in the group 2% to prevent a second oneof these tubes from operating. After the current in the dischargecirouit assumes a steady state, the resistance drop produced by thecommon lement iii? serves to maintain the cathodes of the remainingtubes sufficiently positive to prevent a second one from operating.

Relay 2535 in operating closes a circuit o-ver conductor 23! foroperating in the mechanism 253 a registering or indicating devicepertaining to the tens digit of the line iiiii; and relay 2I5 inoperating closes a circuit over conductor 232 for operating a similarregister in the mechanism 253 pertaining to the units digit of saidline.

It will be noted that only those units tubes are rendered operable whichrepresent the units digits of lines appearing in the particular tenstube that is in operated condition. This provision insures that thecorrect designation of the selected line will always be registered,because it is impossible to register the tens digit of one calling lineand the units digit of a second line which is calling simultaneously.

When it is desired to release the selecting mechanism, relay 22i isoperated in any suitable manner to disconnect the battery 2522 fromconductor 22s. This causes the quenching of the operated tubes 2st andsee and the release of the corresponding relays 255 and 2! 5.

v Fig. 3 shows an alternative circuit arrange ment for operating thetens and units tubes. Only one tube in each group is shown, the No. tenstube 3% and the No. 0 units tube 33L A single line 382 is alsoillustrated, appearing in the start electrode 363 of the tube 300 and inthe start electrode 364 of the units tube 33!. Two relatively highresistors 3G5 and 306 are connected between the line conductor 302 andthe cathode 3G1, and the mid-point of these resistors is extendedthrough a resistor SE28 to the start anode 304. In a similar manner apair of these high resistors are connected between the line conductor ofeach of the ten lines appearing in the tube 388 and the cathode 307, asindicated by the multiple tap 32 I.

When the line calls, relay 369 operates, and a circuit is closed fromthe positive pole of battery 3H1 over conductor SE32 through therelatively low resistor 3!! to ground. The positive potential of thebattery 318 is also impressed over resistor 3 I 2 on the start electrode393. Current also flows over line 392 through resistors 385 and 306,relay 3|3 and the common inductor 3M to ground. This current flowproduces a given potential at the junctor point of resistors 305 and306, and this potential is impressed upon the start electrode 304 of theunits tube 33!. This potential, however, is insufiicient, when added tothe potential impressed on the cathode 3H5 over the phase impulseconductor 3|6, to cause ionization of the tube 3!. As soon as the phaseimpulse is applied over conductor 3|! to the cathode 307 of the tenstube 360, this tube ionizes, and discharge current transfers to the mainanode 3i8. Current now flows from the positive pole of battery 3I9,anode 3|8, cathode 361, winding of relay 3l3, common inductor 3M toground. A positive potential now appears on the cathode 30'! which issufiicient to cause current to flow through the resistor 336, resistor305 and resistor 3 to ground. This current flow causes the appearance ofan additional potential at the junctor point of the resistors 305 and306, and the resultant potential at this point, and therefore thepotential of the start electrode 384, is raised to a value which issufficient to cause the operation of the tube 3! when a phase impulse isapplied to the cathode thereof. When, therefore, the next phase impulseis applied over impulse conductor 3H5, the tube 3M ionizes, and currentflows from the positive pole of battery 322, anode 323, cathode 3I5,winding of relay 324, inductor 325 to ground.

As in the circuits hereinbefore described, the flow of current in thetens tube 3% renders the remaining tens tubes ineffective; likewise theflow of current in the units tube 3lll prevents the operation of asecond one of the units tubes.

If it is desired to reduce the potential applied to the startingelectrode 304 of the units tube, a resistor 320 may be connected asindicated by the dotted line. The fiow of current through resistors 3G8and 320 lowers the potential of the start electrode 304. However, thedifference of the potential on this electrode when the correspondingline is calling and before the tens tube has operated and the potentialon this electrode after the tens tube has operated is sufiiciently greatto insure the selective operation of the units tube only in case thetens tube has operated.

What is claimed is:

1. The combination in a selecting system of a plurality of lines havingdigital designations, a

group of selecting devices corresponding respectively to the digitcharacters of a first digital place of the designations, a second groupof selecting devices corresponding respectively to the digit charactersof a second digital place of the designations, means responsive to aselectable condition on any desired one of said lines for causing theoperation of the particular selecting device of the first grouprepresenting the first-place digit of said line, means effective uponthe oper ation of said device for disabling all other devices of saidfirst group to prevent the operation of a second one thereof in responseto a selectable condition existing simultaneously on a second line,means effective upon the operation of one of said devices for renderingoperative the particular device of said second group representing thesecond-place digit of said desired line, means effective upon theoperation of said particular device of the second group for disablingall other devices of said second group to prevent the operation of asecond one thereof corresponding to a second line having a selectablecondition thereon, and means responsive to the operated devices forselecting and identifying the desired line.

2. The combination in a selecting system of a plurality of lines havingdesignations, said lines being divided into a plurality of groups havingdifierent first-place digit characters, the lines of each group havingdifferent second-place digit characters, a series of selecting devicescorresponding respectively to the first-place digit characters of saiddesignations, a second series of selecting devices correspondingrespectively to the second-place digit characters of said designations,means responsive to a selectable condition on a particular line in anyone of said groups for causing the operation of the selecting devicerepresenting the first-place digit of the lines of said group, meanseffective in response to the operation of said device for disabling allother devices of said first series to prevent the operation of a secondone thereof in response to the selectable condition of a line in thecorresponding group, means effective upon the operation of any one ofthe devices of said first series for rendering operative the particulardevices of said second series representing the second-place digits ofall lines having a selectable condition thereon in the groupcorresponding to the operated device of the first series, meanseffective upon the operation of a particular one of the devices of saidsecond series for disabling all other devices of said second series toprevent the operation of a second one thereof, and means responsive tothe operated device of the first series and the operated device of thesecond series for selecting and identifying the corresponding line.

3. The combination in a selecting system of lines having digitaldesignations, said lines arranged in a plurality of groups havingdifferent first-place digit characters, the lines of each group havingdifferent second-place digit characters, a series of discharge tubescorresponding respectively t the first-place digit characters of saiddesignations, a second series of discharge tubes correspondingrespectively to the secondplace digit characters of said designations,means responsive to the calling condition on any one of said lines forcausing the operation of the discharge tube of the first seriescorresponding to the digital group containing said line, meansresponsive to the flow of discharge current in the operated tube fordisabling the remaining tubes of said first series, means responsive tothe flow of discharge current in the operated tube,

of the first series for rendering operative the tubes of said secondseries, means for operating a tube of said second series correspondingto the second-place digit of the line in the group represented by theoperated tube of the first series, means responsive to the flow ofdischarge current in the operated tube of the second series fordisabling the remaining tubes of said second series, and meanscontrolled by the operated tubes for selecting the corresponding callingline,

4. The combination in a selecting system of a plurality of lines havingdigital designations, said lines divided into a plurality of digitalgroups, a series of discharge tubes corresponding respectively to thedigital groups of lines, a second series of discharge tubescorresponding respectively to the digital designations of the lines ineach group, means for applying a selectable condition to said lines,circuit means for impressing the selectable condition of said lines uponthe corresponding tubes of said first series, means for producingimpulses of a series of phases corresponding respectively to the tubesof both of said series, circuit means for impressing said impulses uponthe tubes of said first series to cause the operation of the first tubetherein having the selectable condition of a line impressed thereon,means responsive to the flow of discharge current in the operated tubefor disabling the remaining tubes of said first series, means responsiveto the flow of discharge current in the operated tube of the firstseries for rendering operative the tubes of said second series, circuitmeans for impressing said impulses upon the tubes of the second seriesto cause the operation of a particular tube therein corresponding to thedigital character of one of the lines having a selectable conditionthereon in the group corresponding to the operated tube of the firstseries, means responsive to the flow of discharge current in theoperated tube of said second series for disabling the remaining tubes ofsaid second series, and means for identifying the line corresponding tothe operated tubes of the first and second series.

5. The combination in a selecting system of a plurality of lines dividedinto tens groups, the lines of each group having different unitsdesignations, a series of tens digit tubes, one for each tens group,each of said tubes having an electrode individual to each line in thegroup, a series of units digit tubes, one for each units designation ineach group, each units tube having an electrode individual to a line ineach of the ten groups, means for creating a calling condition on saidlines, circuit means for impressing the calling condition of each lineupon the corresponding electrodes of the corresponding tens tubes, meansfor producing impulses of difierent phases, said phases correspondingrespectively with the tubes of both series, circuit means for impressingsaid impulses upon the tubes of the tens series to cause the operationof the first tube thereof having electrodes with the calling conditionof one or more lines impressed thereon, means responsive to the fiow ofdischarge current in the operated tens tube for disabling the remainingtens tubes, the flow of discharge current in the operated tens tube alsoserving to alter the potential of the electrodes thereof to impress anoperative potential upon the electrodes of the tubes of said unitsseries, circuit means for impressing said phase impulses upon said unitstube to cause the operation of the particular tube therein upon which anoperative potential has been impressed by the electrode of the operatedtens tube, means efiective in response to the flow of discharge currentin the operated units tube for disabling the remaining units tubes toprevent the operation of a second one thereof corresponding to the unitsdesignation of a second line in the selected group having a callingcondition thereon, and means responsive to the operation of the tenstube corresponding to the selected line group and to the operation ofthe units tube corresponding to the units designation of a particularline in said selected group for identifying said particular line.

WILLIAM H. T. HOLDEN.

